This invention relates to a process for preparing 4-(D-3-amino-3-carboxypropoxy)phenylglyoxylic acid oxime in the form of an amino-protected ester and to intermediates useful therein. In particular, this invention relates to a stereospecific synthesis of the 3-acyl side chain portion of the .beta.-lactam antibiotic FR 1923. Antibiotic FR 1923, nocardicin, is represented by the following structural formula ##STR1##
The antibiotic is described in Belgian Pat. No. 830934 and by H. Aoki et al., 15th Interscience Conference on Antimicrobial Agents and Chemotherapy, Abstract No. 97, September, 1975.
FR 1923 has previously been prepared by culturing Nocardia uniformis var. tsuyamanensis ATCC 21806 in aqueous nutrient media, isolating the antibiotic substance from the fermentation broth and purifying the isolate.
The product obtained in the process of this invention and certain derivatives thereof are useful in the total chemical synthesis of FR 1923 as described in co-pending application Ser. No. 739,161, filed Nov. 5, 1976, now U.S. Pat. No. 4,158,004. As disclosed therein, the nucleus of FR 1923, 1-(.alpha.-carboxy-4-hydroxybenzyl)-3-amino-2-azetidinone and preferably an ester thereof represented by the formula ##STR2## is acylated with an esterified and amino-protected active carboxylic acid derivative of 4-(D-3-amino-3-carboxypropoxy)-phenylglyoxylic acid oxime. After acylation, the ester groups are de-esterified and the amino-protecting group of the side chain is removed to provide the antibiotic FR 1923.